Syntheses, Structures, and Spectroscopic Properties of Plutonium and Americium Phosphites and the Redetermination of the Ionic Radii of Pu(III) and Am(III)

A series of isotypic rare earth phosphites (RE = Ce­(III),
Pr­(III),
Nd­(III), Pu­(III), or Am­(III)) with the general formulas RE2(HPO3)3(H2O) along with a Pu­(IV)
phosphite, Pu­[(HPO3)2(H2O)2], have been prepared hydrothermally via reactions of RECl3 with phosphorous acid. The structure of RE2(HPO3)3(H2O) features a face-sharing interaction
of eight- and nine-coordinate rare earth polyhedra. By use of the
crystallographic data from the isotypic series along with data from
previously reported isotypic series, the ionic radii
for higher coordinate Pu­(III) and Am­(III) were calculated. The VIIIPu­(III) radius was calculated as 1.112 ± 0.004 Å,
and the IXPu­(III) radius was calculated to be 1.165 ±
0.002 Å. The VIIIAm­(III) radius was calculated as
1.108 ± 0.004 Å, and the IXAm­(III) radius was
calculated as 1.162 ± 0.002 Å.